Search Results (298)

A one-dimensional Thue–Morse graphene photonic crystal (1D TMGPC) composed of alternating identical dielectric layers and graphene sheets is proposed, in which two distinct graphene chemical potentials are arranged according to a Thue–Morse quasi-periodic sequence. Using the transfer matrix method, we demonstrate that this structure effectively modulates terahertz waves and generates multiple abundant photonic bandgaps at both 20 K and 300 K. Notably, a novel splitting of low-frequency bandgaps produces two additional omnidirectional and polarization-insensitive bandgaps centered at approximately 1.45 THz and 1.95 THz. By analyzing the dispersion relations, reflection phase, photonic density of states, and electric field distributions, the boundary-driven modulation mechanism associated with the quasi-periodic chemical potential is elucidated. Furthermore, the proposed structure exhibits excellent multi-dimensional tunability. The bandgap properties can be dynamically tuned via the electrical control of graphene chemical potentials without altering the physical geometry. Structural tailoring provides an additional degree of freedom, as increasing the Thue–Morse sequence order induces passband splitting. Additionally, increasing the number of repeating periods yields comb-like multi-channel narrowband filtering responses. At a cryogenic temperature of 20 K, two distinct multi-channel narrowband comb filtering responses appear in the frequency ranges of 1.20–1.33 THz and 4.10–4.80 THz, with a minimum full width at half maximum (FWHM) of 1.10 GHz. At a room temperature of 300 K, the higher-frequency comb filtering response remains in the range of 4.10–4.80 THz, with a minimum FWHM of 5.70 GHz. Moreover, we evaluate the performance and stability of the structure when employed as filters and electro-optic switches, thereby providing useful insights for terahertz applications. With its simple geometry, abundant bandgaps, and flexible electro-structural tunability, the proposed 1D TMGPC is highly promising for broadband and electrically tunable terahertz devices. Full article

Iron oxychloride (FeOCl) has recently attracted considerable attention as a high-performance heterogeneous Fenton-like catalyst. Its layered Fe-O-Cl coordination environment enables rapid FeIII/FeII redox cycling and efficient activation of H₂O₂, thereby promoting the generation of reactive oxygen species (ROS) for pollutant degradation. This review summarizes recent progress in FeOCl-based materials, including their crystal structure, optical, electrochemical, magnetic and other physicochemical properties, synthesis strategies, catalytic mechanisms, and environmental applications, with particular emphasis on experimental evidence and density functional theory (DFT) calculations. Special attention is given to pH-insensitive H₂O₂ activation, visible-light-assisted Fenton-like reactions, heterojunction construction, elemental doping, intercalation engineering, membrane-supported catalysts, morphology engineering, and flow-through electro-Fenton configurations. FeOCl-based catalysts have demonstrated outstanding performance in degrading dyes, antibiotics, phenolic compounds, endocrine-disrupting compounds, and other recalcitrant pollutants, while also showing potential in heavy-metal adsorption, selective oxidation, and energy-related applications. Finally, remaining challenges concerning catalyst stability, iron leaching, scalable synthesis, realistic water matrices, byproduct toxicity, and reactor integration are discussed to guide the rational design of practical FeOCl-based catalytic systems. Full article

Polymer-stabilized liquid crystal (PSLC) films are promising for smart window applications because of their transparent-to-scattering switching behavior. However, conventional acrylate-based PSLC films often suffer from poor mechanical robustness and weak interfacial adhesion, limiting their use in flexible devices. Herein, epoxy-based PSLC films have been prepared through radical-promoted cationic photopolymerization using a difunctional epoxy monomer, E6M, and a series of liquid-crystalline monoepoxy monomers, E-nOCB. The effects of alkyl chain parity, chain length, and E6M/E-10OCB ratio on polymer morphology, electro-optical behavior, and peel strength were systematically investigated. Even-numbered E-nOCB monomers favored the formation of regular columnar polymer structures and improved optical contrast, whereas odd-numbered monomers produced more disordered networks with higher peel strength. Among them, the sample prepared with E-10OCB showed a better balance between electro-optical performance and mechanical adhesion. At a fixed total polymer content of 15 wt%, optimizing the E6M/E-10OCB ratio enabled the sample doped with E-10OCB to achieve the highest contrast ratio of 160.91 while increasing the peel strength from 47.28 to 55.69 kPa compared with the sample without E-10nOCB. These results demonstrate that regulating monoepoxy/diepoxy composition and alkyl chain structure is an effective strategy for improving the overall performance of epoxy-based PSLC films for smart windows. Full article

Mechanized harvesting in the industrial tomato sector is currently bottlenecked by excessive mechanical injuries and elevated levels of foreign materials generated during electro-mechanical combine harvesting operations. To combat these limitations, this comprehensive review explores recent breakthroughs in harvester-mounted smart grading systems engineered specifically for complex, open-field conditions. Rather than relying solely on conventional optical inspection, the study examines the transition toward advanced, heterogeneous edge-computing frameworks—incorporating FPGAs and embedded GPUs—deployed within electro-mechanical harvesting platforms. This architectural evolution plays a crucial role in mitigating unpredictable processing delays caused by intense operational vibrations, although achieving absolute real-time stability under extreme field conditions remains an ongoing challenge. To minimize bruising and physical deterioration, our analysis synthesizes findings from multi-scale explicit dynamic finite element simulations, unpacking the underlying microstructural failure modes of the crop. We illustrate how regulating applied forces via soft robotic effectors can help approach a ‘damage-free’ handling threshold, though empirical results vary depending on fruit maturity and dynamic operational speeds. Furthermore, coupling multi-modal sensor fusion with Convolutional Neural Networks (CNNs) shows promising potential for non-destructive internal property evaluation under the vibration, dust, and throughput constraints of electro-mechanical harvesters, pending broader validation across diverse field datasets. Ultimately, by projecting future trends in onboard electro-mechanical harvester separation and advocating for a closer synergy between agronomic practices and machine engineering, this paper delivers a comprehensive blueprint for building next-generation, highly resilient, and gentle sorting machinery. Full article

Electro-optic frequency combs (EOFCs), generated through the microwave-driven modulation of continuous-wave lasers, have emerged as a highly reconfigurable and system-compatible class of optical frequency combs with growing importance in microwave photonics, coherent communications, spectroscopy, and precision metrology. In contrast to mode-locked lasers and Kerr microresonator combs, EOFCs offer electrically programmable repetition rates, deterministic phase coherence, and intrinsic compatibility with radiofrequency electronic systems, making them particularly attractive for integrated and application-oriented implementations. As EOFCs evolve toward broader bandwidths, lower power consumption, and full on-chip integration, their achievable performance is increasingly constrained by the interplay between electro-optic physical mechanisms, modulator architectures, and material platform properties. This review establishes a unified analytical framework that systematically connects EOFC generation mechanisms, device configurations, key performance metrics, and platform-level limitations. We first summarize the fundamental electro-optic effects underpinning EOFC generation and analytically examine representative modulator architectures, including phase modulators, Mach–Zehnder modulators, and microresonator-based schemes, to clarify their respective comb-generation characteristics. Key performance determinants, such as modulation depth, bandwidth, electro-optic efficiency, and optical loss, are then discussed to elucidate their coupled influence on comb-line count, spectral flatness, output power, and phase noise. Subsequently, the performance of EOFCs implemented on major integrated platforms, including Silicon on Insulator (SOI), Indium Phosphide on Insulator (InPOI), Lithium Niobate on Insulator (LNOI), and Lithium Tantalate on Insulator (LTOI), is comparatively reviewed to highlight the material-dependent advantages and constraints. Finally, emerging directions based on heterogeneous integration and ferroelectric materials with ultrahigh electro-optic coefficients are discussed as promising pathways to overcome the current performance bottlenecks. This review provides clear physical insights and engineering guidance for the future development of high-performance, integrated EOFC systems. Full article

Graphene oxide (GO) was employed as an additive to improve the electrochemical activity of zinc oxide (ZnO) used as both a photoelectrocatalyst for water splitting and an electrochemical sensor for detection of diclofenac. To comprehend the influence of a small amount of GO on the electrochemical activity of ZnO, a series of ZnO/xGO (x = 0, 0.1, and 0.5) particles was synthesized by microwave processing of Zn(OH)₂ precipitate in the presence of 0.1 and 0.5 wt.% of previously prepared GO. The phase composition and crystal structure ordering of ZnO/xGO particles were investigated by XRD and Raman spectroscopy. The optical properties were studied by UV–Vis DRS and PL spectroscopy. The particle morphology was inspected by FE–SEM while the textural properties were analyzed by the low-temperature nitrogen adsorption–desorption method. The (photo)electrocatalytic and electrochemical sensing activities were examined on the ZnO/rxGO modified glassy carbon electrodes (GCEs) prepared by in situ reduction of the ZnO/xGO modified GCEs for 120 s. The electro- and photoelectrocatalytic activity of ZnO/rxGO modified GCEs for water splitting was tested in dark conditions and after 60 min under illumination, respectively, employing linear sweep voltammetry in 0.1 M NaOH and 0.1 M H₂SO₄ as electrolytes. The electrochemical sensing activity of ZnO/rxGO modified GCEs was tested for detection of diclofenac in aqueous solution. The improvement in the electrochemical activity of ZnO was correlated with the added amount of GO, structural defects, and particle morphology. Full article

Traditional polymer-dispersed liquid crystal (PDLC) faces limitations in smart dimming applications due to high driving voltage and poor high-temperature stability. In this study, a high-birefringence liquid crystal (QYPDLC-901) was used to prepare PDLC films with liquid crystal contents ranging from 72 wt% to 80 wt%, achieved through synergistic regulation of a low-functional acrylic polymer system and a low-intensity curing process. The effects of liquid crystal content, cell gap, and temperature on electro-optical properties were systematically investigated. Optimal performance was obtained at a liquid crystal content of 77 wt%, with a low threshold voltage of 2.9 V, saturation voltage of 7 V, fast response (rise time 4.2 ms, decay time 47 ms), and a favorable balance between high on-state and low off-state transmittance. Microstructural analysis revealed that the superior performance results from uniform droplet dispersion and low interfacial energy. Furthermore, the PDLC exhibited excellent switching stability from 23 °C to 90 °C, maintaining a maximum transmittance of 93% at 90 °C, with increases of only 0.4 V in threshold voltage and 0.1 V in saturation voltage. This study provides an experimental basis for designing smart dimming devices suitable for low-voltage driving and extreme environments. Full article

Applying a constant external electric field to a semiconductor nanostructure with Wannier–Mott excitons, in which the electron and hole interact via a centrally symmetric Coulomb potential, alters the symmetry of the system. When the electric field is applied parallel to the z-axis, the system exhibits cylindrical symmetry; when the field lies in the $x-y$ plane, the symmetry is broken. These symmetry changes affect the optical properties of the system. We present a theoretical calculation that yields analytical expressions for the optical functions of CdSe Nanoplatelets—reflectivity, transmissivity, and the absorption coefficient—in an external homogeneous electric field. From these, we focus on the absorption coefficient. We consider various configurations, with the external field oriented perpendicular and parallel to the platelet planes. Using the real density matrix approach, we calculate the linear electro-optical functions of CdSe nanoplatelets, taking into account the effect of dielectric confinement on excitonic states. We also discuss the impact of platelet geometry (thickness and lateral dimensions) and applied field strength on the spectrum. Full article

Reduced graphene oxide (rGO) has attracted interest as a potential, cost-effective alternative to graphene layers produced by single-crystal thin-film growth techniques. Its solubility in various solvents, the ability to tune its optical and electrical properties, the ability to manipulate the optoelectronic properties of rGO-based heterojunctions, and the possibility of depositing it on flexible substrates broaden its potential applications, from electro-optical communications to environmental monitoring. In this work, we present a characterization of reduced graphene oxide (rGO) deposited on p-type Si₃N₄/Si substrate using different techniques such as Raman spectroscopy, optical transmittance, and current-voltage measurements under dark and illuminated conditions in the 400–700 nm range. Furthermore, the temperature dependence of the photocurrent of the rGO-based photoconductive device was studied in the temperature range from 300 K to 77 K. It has been shown that the electron transport mechanism through the p-type rGO/SiN/Si heterojunction at low voltage involves mainly a hopping process at 77 K and a thermionic mechanism at room temperature. Furthermore, the Fowler–Nordheim tunneling and trap-limiting mechanisms allow the presence of charge carriers in the device at both temperatures. Estimation of the main figures of merit, responsivity, detectivity, and NEP, shows an improvement in photodetection performance at low temperatures. Full article

Hot-spots represent a significant failure mechanism in photovoltaic (PV) modules, typically attributable to electrical mismatching. However, thermo-optical degradation of the encapsulant, including discoloration and delamination, can both trigger and amplify mismatch by inducing localized optical losses and temperature rise. The present paper proposes a compact circuit-level electro-thermal–optical model that explicitly captures the short-term closed-loop interaction between mismatching, cell temperature, and temperature-dependent optical properties. The photogenerated current is formulated as a function of irradiance, cell temperature, and encapsulant degradation, enabling dynamic feedback between heating and optical losses. Numerical simulations are carried out on a commercial 40-cell PV module under four representative operating static scenarios. The results demonstrate that, even in the absence of shading, optical degradation can generate multimodal P–V characteristics, drive cells into reverse bias, and produce hot-spots. When optical degradation coexists with irradiance mismatch, the feedback loop significantly amplifies mismatching and shifts the maximum power point toward thermally unsafe operating conditions. These findings demonstrate that maximizing instantaneous power does not necessarily maximize lifetime energy yield, underscoring the need for thermal-aware MPPT strategies and providing a practical framework for early detection of thermo-optical faults in PV modules. Full article

Aniline (ANI) was electropolymerized on ITO substrates with different surface resistivities. The process was performed by cyclic voltammetry from an aqueous, homogeneous solution containing sulfuric acid and the aniline monomer using various numbers of cycles and scan rates. The resulting polymer films (PANI) were characterized by ATR-IR spectroscopy, spectroscopic ellipsometry and atomic force microscopy. The influence of ITO surface resistivity on the electropolymerization process, the quality of the obtained PANI layers, and their optical properties was evaluated. Homogeneous PANI films were produced on ITO substrates with surface resistivities of 15–25 Ω/sq, encompassing both emeraldine salt and emeraldine base forms. Although the film’s growth was rapid, it also led to adhesion issues. In contrast, for ITO substrates with surface resistivities of 70–100 Ω/sq and 80–100 Ω/sq, the resulting films showed improved adhesion but were less homogeneous. Nevertheless, the conductive emeraldine salt form of polyaniline was successfully obtained. The conductive form of polyaniline was obtained without any additional modifications to the electropolymerization procedure. Notably, the literature provides no systematic analysis of electropolymerization on ITO substrates with different surface resistivities, which opens up new research opportunities and provides a basis for the rational design and optimization of PANI-based electro-optical coatings for advanced sensing applications. Full article

Lead-free transparent ferroelectric ceramics with integrated opto-electro-mechanical functionalities are pivotal for next-generation multifunctional devices. In this study, K_0.48Na_0.52NbO₃-xLa₂O₃ (KNN-xLa, x = 0.005 − 0.04) ceramics were fabricated via a conventional solid-state route to investigate the La³⁺-induced multiscale structural evolution and its modulation of optical and electrical properties. La³⁺ substitution drives a critical structural transition from an anisotropic orthorhombic phase (Amm2) to a high-symmetry pseudocubic-like tetragonal phase (P4mm) for x ≥ 0.025, characterized by minimal lattice distortion (c/a = 1.0052). This enhanced structural isotropy, coupled with submicron grain refinement (<1 μm) driven by ${\mathrm{V}}_{\mathrm{A}}^{\prime }$-mediated solute drag, effectively suppresses light scattering. Consequently, a high-transparency plateau (T₇₈₀ ≈ 53–58%, T₁₇₀₀ ≈ 70–72%) is achieved for 0.025 ≤ x ≤ 0.035. Simultaneously, the system undergoes a crossover from normal ferroelectric (FE) to relaxor (RF) state, governed by an FE–RF boundary at x = 0.015. While x = 0.005 exhibits robust piezoelectricity (d₃₃ ≈ 92 pC/N), the x = 0.015 composition facilitates a transitional polar state with large strain (0.179%) and high polarization (P_m ≈ 33.3 μC/cm², P_r ≈ 15.8 μC/cm²). Piezoresponse force microscopy (PFM) confirms the domain evolution from lamellar macro-domains to speckle-like polar nanoregions (PNRs), elucidating the intrinsic trade-off between optical transparency and piezoelectricity. This work underscores La³⁺ as a potent structural modifier for tailoring phase boundaries and defect chemistry, providing a cost-effective framework for developing high-performance transparent electromechanical materials. Full article

The purpose of this research is to examine how the electro-optical behavior of platinum (Pt) nanoparticles prepared via the gamma radiolysis process is related to both the radiation dose and to the Pt precursor concentration. The Pt precursor used in these experiments has been radiolytically degraded using a ⁶⁰Co gamma source at dosages ranging from 80 kGy to 120 kGy. As well, varying the concentration of the Pt precursor from 5.0 × 10⁻⁴ M to 20.0 × 10⁻⁴ M was carried out as a systematic investigation. Spectrophotometric analysis utilizing UV–Visible spectroscopy and TEM provided the optical data and particle size information for the nanoparticles. The results indicate that increasing the radiation dosage results in smaller Pt nanoparticle sizes due to an increased rate of nucleation and that increasing the Pt precursor concentration leads to larger Pt nanoparticles due to an increase in ion recombination. Both the dose and concentration dependency of the optical absorption spectrum indicate a significant relationship between size and plasmon behavior. Also, the conduction band energy level, which was determined from the maximum of the UV–Visible absorption peak, is dependent on the particle size and shows a pronounced quantum confinement effect, with the conduction band energy increasing as the particle size decreases. Thus, these studies provide a definitive correlation of structure–property in Pt nanoparticles and confirm the capability of the gamma radiolytic synthesis process to be used for controlling the specific electronic and optical properties of Pt nanoparticles. Full article

The polymer dispersed liquid crystals (PDLCs) with conical boundary conditions are considered. PDLC films with different values of the relative chirality parameter $N_0$ of chiral nematic droplets ranging from 0 to $1.32$ are studied experimentally and theoretically. In flattened spheroid-shaped chiral nematic droplets, a twisted axial-bipolar structure is formed whose twist angle increases with rising $N_0$ value. Two stable states of the structure are revealed: one with the bipolar axis oriented perpendicular to the short axis of the spheroid and another with the bipolar axis oriented parallel to it. Applying a small voltage causes the bipolar axes of the chiral nematic droplets to reorient parallel to the electric field. The structure is unwound in strong electric fields, and the droplet order parameter reaches a high value of nearly $0.95$. These features of the voltage-induced reorientation of the axial-bipolar structure explain the experimentally observed characteristic electro-optical properties of PDLC cells: high transmittance $T^{\max }\cong 0.90$ in the on-state and low control voltages of less than 35 V. The minimum transmittance of the PDLC cells decreases as the value of $N_0$ increases; for samples with $N_0\ge 0.60$, the contrast ratio exceeds 145. Full article

The interaction of an ultra-short, high-power laser pulse with a solid target, in the so-called Target Normal Sheath Acceleration (TNSA) configuration, produces particles in the MeV range. Fast electrons can escape from the target after the interaction, inducing electrostatic fields on the order of TV/m close to the target surface. These fields accelerate MeV protons and heavy ions at the rear of the target, allowing them to escape. The complete process is difficult to probe, as it occurs on the sub-ps timescale. At the INFN-LNF SPARC_LAB test facility, single-shot diagnostics such as the Electro-Optic Sampling (EOS) are being developed and tested for time-resolved direct measurements of the produced electrons and associated longitudinal electric fields. Electrons are the core of the process, and their properties determine the following production of positive charge particles and electromagnetic radiation. Different target geometries and materials are being investigated to analyze the enhancement of fast electron emission and the correlation with positive charge production. Simultaneous observations of electron and proton beams have been performed using two diagnostic lines, the EOS for electrons and a time-of-flight (TOF) detector for protons. This work provides an overview of the previous experiments performed at SPARC_LAB dedicated to the TNSA characterization. Full article